Cushing's disease is one of the most difficult diagnoses to establish in pediatric endocrinology. Once made, transsphenoidal surgery (TSS) is considered the treatment of choice, with many reports suggesting extremely high cure rate. However, we have established that the diagnosis is not readily made in a subset of pediatric patients, and that the "cure" rate following TSS is not as high in our population as previous reports might suggest. The purpose of this study is to determine: 1) the best study(ies) to establish the diagnosis of Cushing's disease; 2) long-term "cure" rate following TSS; 3) complications from the procedure; 4) the best means to predict relapse; 5) long term sequelae of Cushing's disease and of the surgical procedure. We hypothesize that a) relapse in children may be higher than previously considered, and b) long-term consequences are primarily manifested by failure to fully recover bone mineral density, as well as compromised final adult height.